Electrical protective device



C. LE 6. FORTESCUE. ELECTRICAL PROTECTIVE DEVICE.

APPLICATION FILED APR-4. ma.

1 344,759. Patented June 29, 1920.

VO/tdye of Condenser furrenzinfle/d may at win my WITNESSES: INVENTOR ilk (Piaf/e5 LeG/rtescue BY 3 AT'ToRNEY UNITED STATES PATENT OFFICE.

CHARLES LE G. FORTESCUE, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR T0 WEST- INGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENN- SYL'VANIA.

Application filed April 4, 1918.

To all whom it may concern:

Be it known that I, CHARLES LE G. Fon- TESCU'E, subject of the King of Great Britain, and a resident of Pittsburgh, in the county of Allegheny and State of Penns lvania, have invented a new and useful mprovement in Electrical Protective Devices, of which the following is a specification.

My invention relates to electrical protective devices and particularly to means for quickly decnergizing the field-magnet winding of a direct-current generator.

One object of my invention is to provide means for dissipating the electromagnetic energy of the field-magnet winding of a generator in a minimum period of time after the generator becomes short circuited.

A further object of my invention is to provide a device of the above-indicated character that shall be simple and inexpen sive to construct and effective in its oper ation.

In practising my invention, I provided a condenser for automatically absorbing the electromagnetic energy of the field-magnet winding of a generator when the generator becomes short circuited Means is also provided for rendering the condenser ineflective a predetermined interval of time after the energy discharges through the same. This interval of time is such that the condenser is fully charged at the instant that no current traverses the field-magnet winding. If this time of operation is such that no current traverses the field-magnet winding at the instant the condenser 1s fully charged, the winding-is demagnetized in a minimum period of time without disrupting the insulation thereof by reason of a sudden collapse of voltage thereon.

Figure 1 of the accompanying drawings is a diagrammatic view of an electric circuit embodying my invention, and Fig. 2 is a diagram illustrating the relation of the current traversing the fieldma'gnet winding and the voltage of a condenser.

A direct-current generator 1, comprisingan armature 2 and field-magnet windings 3, is operatively connected to a distributing circuit 4. The field-magnet windings 3 arev connected, through a circuit interrupter 5, to an exciter generator 6. A condenser 7 Specification of Letters Patent.

Patented June 29, 1920.

Serial No. 226,633.

is connected across the terminals of the field-magnet windings 3, and a short-circuitlng device 8 is provided for the condenser 7.

The movable member 9 of the circuit interrupter 5 is mounted at one end of a pivotally-mounted lever arm 10 the other end of which is adapted to be held in position by a latch 11 against the action of a spring 1?. The movable member 13 of the shortcircultlng device 8 is mounted adjacent the latched end of the lever arm 10, and an electromagnet 14- is provided for actuating the latch 11, when the voltage across the circuit 4 changes quickly by reason of a fault therein. The electromagnet 14 is connected 1n series with a condenser 15 and the circult, thus constituted, is connected across the circuit 4. The condenser 15 is of such characteristics that it is adapted to discharge when the voltage across the circuit 4 changes suddenly.

When a short circuit occurs on the circuit 4: the electromagnet 4 is energized to actuate the latch 11 and this permits the spring 12 to open the circuit interrupter 5. The opening of the interrupter 5 disconnects the exciter generator 6 from the fieldmagnet windings 3 and permits the electromagnetic energy of the same to charge the condenser 7. The period of the discharge oscillation will be T=21r /IIC discharged in a time Consequently,

4 if the time between the opening of the circuit interrupter 5 and the elos ing of the short-circuiting device 8 is equal to the condenser 7 will be charged to its full capacity at the instant that no current traverses the field-magnet windings 3. Thus, if the condenser is rendered ineffective by reason of the same being short circuited at this instant, the field-magnet winding 3 will he deenergized in a minimum period of time without disrupting the in- 105 sulation of the same.

magnet winding during the time and,

since, at the expiration of this time, no current traverses the field-magnet winding 3, it ma be safe to either disconnect the condenser or short circuit the same as shown in Fig. 1 of the drawings, without impairing the insulation of the field-magnet wind- $3 invention is not limited to the specific type of operating mechanism illustrated, as various modifications may be made therein Without departing from the spirit and scope of the same, as set forth in the appended claims.

I claim as my invention:

1. The combination with a generator and an exciter therefor, of a condenser connected across the field-magnet winding of the generator, and means for disconnecting the exciter from the field-magnet winding of the generator when a short circuit occurs on the generator and for short circuiting the condenser a predetermined interval of time after the exciter is disconnected.

2. The combination with a generutorand an exciter therefor, of a condenser connected across the field-ma net winding of the generator, and means or disconnecting the exciter from the field-magnet winding of the generator when the voltage across the generator changes quickly and for short circuiting the condenser a predetermined interval of time after the exciter is disconneoted.

3. The combination with a generator and an exciter therefor, of a condenser connected across the field-magnet winding of the generator, and means for disconnecting the exciter from the fieldmagnet winding of the generator when the voltage across the enerator changes quickly and for renderng the condenser ineffective to discharge through the field-magnet winding a predetel-mined interval of time after the exciter is disconnected.

4. The combination with a generator and an exciter therefor, of a condenser for absorbing the electromagnetic energy of the field-magnet winding of the generator when the excite! is disconnected therefrom, and means for short-circuitin said condenser under predetermined con itions.

5. The combination with a generator and an exciter therefor, of means for absorbing the electromagnetic energy of the field-magnet Winding of the generator when the exciter is disconnected therefrom, and means for short-circuiting said absorbing means a predetermined interval of time after the exciter is disconnected.

6. The combination with a generator and an exciter therefor, of a condenser connected across the fieldanagnet winding of the generator, a circuit interrupter for disconnecting the excitcr when a short circuit occurs on the generator, and means actuated a predetermined interval of time after the op eration of the circuit interrupter for precluding the discharge of the condenser through the field-magnet winding of the generator.

7. The combination with a generator and an exciter therefor, of a condenser connected across the field-magnet winding of the generator, a circuit interrupter for disconnesting the exciter when a short circuit occurs on the generator, and means actuated a predetermined interval of time after the operation of the circuit interrupter for short circuiting the condenser.

8. The combination with a generator and an exciter therefor, of a condenser connect ed across the field-magnet winding of the generator, a circuit interrupter for disconnecting the exciter when a short circuit occurs on the generator, and means for short circuiting the condenser a suflicient interval of time after the exciter is disconnected to cause no current to traverse the fieldmagnet winding of the generator.

9. The combination with a generator and an exciter therefor, of a condenser connected across the field-magnet winding of the generator, a circuit interrupter for disconnecting the exciter when a short circuit occurs-on the generator, and means for shortcircuiting the condenser at the instant no current traverses the field-magnet winding of the nerator.

10. he combination with a generator and an exciter therefor, of a condenser for absorbing the electro-magnetic energy of the field-magnet winding of the generator when the exciter is disconnected therefrom, and means for short-circuiting the condenser a predeterminedinterval of time after the exciter is disconnected.

11. The combination with a enerator and an exciter therefor, of means or absorbing the electromagnetic energy of the field-magnet winding of the generator, for disconnecting the exciter therefrom when the voltage across the generator changes quickly and for short-circuiting the absorbing means.

In testimony whereof I have hereunto subscribed my name this 19th day of March CHARLES LE G. FDRTESGUE. 

